1. Field of the Invention
The present invention relates to a front and rear drive power distribution control device for a vehicle, provided with a limited slip differential mechanism between front and rear drive shafts.
2. Description of Related Art
Conventionally, on a vehicle provided with a front and rear drive power distribution control device, with respect to vehicle dynamic performance, it is generally known that cornering performance tends to be suppressed and traction performance tends to be improved, if limited differential torque between front and rear drive shafts is increased. Given this situation, for example, Japanese patent laid-open No. 2004-225716 discloses a technique, in a four-wheel-drive vehicle having front and rear drive power distribution control using engaging torque of a clutch, to improve both cornering performance and traction, by estimating torque input from an engine side, and including both a control unit for controlling front and rear drive power distribution based on this input torque and a limited slip differential mechanism between front and rear drive shafts.
However, as disclosed in Japanese patent laid open No. 2004-225716 described above, when including both control unit and limited slip differential mechanism, if a control value is supplied from the control unit without taking into consideration limited differential torque generated in the limited slip differential mechanism, clutch engaging torque for performing overall front and rear drive power distribution is not set accurately, and there is a fear that target vehicle behavior cannot be obtained.
The present invention has been conceived in view of the above described situation, and an object of the present invention is to provide, in a four-wheel-drive vehicle including both a control unit and a limited slip differential mechanism, a front and rear drive power distribution control device that can accurately set clutch engaging torque for carrying out front and rear drive power distribution, and can improve both cornering performance and traction performance.